Pneumatically actuated valves are commonly used to control the flow of fluids where remote operation is desired. Examples include utilization in automated processes and hazardous locations. Pressurized air supplying systems for pneumatic controls are typically limited to a maximum pressure of 80-100 psig. Because of this low pneumatic control pressure, pneumatic valve actuators, and especially those that control high pressure fluids through an associated valve, are typically very large in physical size. The large size is necessary to provide a sufficiently large surface area upon which the pneumatic pressure works to generate sufficient force to control the flow of fluid through the associated valve. At higher fluid pressures, a proportionally higher force is needed to maintain control.
Typical pneumatic valve actuators consist of a single or multiple piston design. Pneumatic pressure acting on the piston(s) exposed surface area determines actuator force. Pneumatic valve actuators, and particularly the larger size actuators, pose problems for system designers of fluid distribution systems. Due to exhaust requirements, space constraints, and/or other possible factors, it is greatly desirable to minimize the physical size of these pneumatic valve actuators without reducing their ability to generate actuation force or sacrificing valve performance.
Known actuators are disclosed in U.S. Pat. Nos. 4,684,103; 4,875,404; and 5,253,671 wherein attempts have been made to reduce the actuator's size by utilizing a force multiplying mechanism to generate high forces relative to actuator size. Although the size of these actuators is somewhat reduced, the reductions in size come with inherent disadvantages. The force multiplying mechanism in each of these actuators consumes a substantially large portion of the actuator size and resultantly limits the overall size reduction permitted of the actuator. Also, the force multiplying mechanism in each of these actuators requires an increase in the number of moving parts within the actuator. These additional moving parts increase actuator complexity and decrease its overall reliability.
Responsive to the above described deficiencies associated with the use of known pneumatic force multiplication actuator systems, the present invention has been developed to alleviate these drawbacks and provide further benefits to the user. These enhancements and benefits are described in greater detail herein below with respect to several alternative embodiments of the present invention.